The scope of this project was to analyze for the presence of N-acetyltransferase (NAT) in rat retina. Previous investigators had detected in rat retina the enzyme hydroxyindole-O-methyltransferase (H1OMT) and the hormone melatonin. Therefore, to confirm that melatonin could be synthesized in this tissue, it was necessary to confirm the presence of NAT. Present results showed that NAT is present but only at less than 10% of that detected in rat pineal. Maximal activity (204 pmol/retina/10' or 115 pmol/mg protein/10') occurred at midnight. TLC with two different solvent systems confimed that the product formed from labelled acetyl CoA and 5-hydroxytryptamine was labelled N-acetyltryptamine.